Grain drills and planters form a slit or furrow in the ground, deposit seed in the slit, and cover the seed with soil. The soil that covers the seed is often compacted by a press wheel. The seed covering portion of planting is relatively simple when the field has been cultivated and there is little or no residue from the previous crop. The seed covering portion of the planting process may be very difficult when the field has not been cultivated, and the surface is covered with a thick mat of crop residue from an earlier crop or crops that were grown in the field.
Planters and grain drills, that are planting crops in a cultivated field, form ridges of loose soil between the furrows that seed is deposited in. A press wheel that rolls down the furrow after seed is deposited in the furrow, tends to force soil from the sides of the ridges down on top of the seed dispensed in the furrow. At the same time, soil is moved over the seed, the soil above the seeds is compacted. In some cases, too much soil is deposited on top of the seeds, and plants are not able to grow up through the soil that covers them. Compacted soil above seeds tends to form a hard crust as it dries following a rain. Seed that has germinated is frequently unable to emerge through such a crust and dies, even if the crust is relatively thin. Implements such as rotary hoes have been developed to break up crusted soil so that plants can emerge. Unfortunately, rotary hoes cannot always break up crusted soil. In many cases, a hard crust that forms above seeds after a rain will kill the seeds and make it necessary to replant the field.
Planters and grain drills that plant crops in fields subjected to no till or minimum tillage farming practices also have problems covering the seed with soil. Seed which is not covered with soil and is exposed to the sun and air will generally not germinate. Press wheels merely roll on the surface of the soil and cannot move compacted soil, at the sides of the slit that receives the seed, down into the slits to cover the seed.
Discs have been employed at either one or both sides of a furrow to form a new furrow and to cover the seeds with a ridge of soil. Such discs can place too much soil on top of seed. When such discs are employed in fields with some surface residue, they tend to ride up over some residue and not cover seeds at times. At other times, they tend to cover seeds with too much soil.
Coulters with fluted blades are frequently employed on drills and planters in, front of the assembly that forms a slit or furrow and deposits seed in the furrow, to cut old crop residue. By cutting through the residue in front of a furrow forming and seed placement assembly, the furrow forming assembly is able to penetrate the soil and place seed at the desired depth. To cover the seed and fill the seed furrow with a closing disk, the disc has to be positioned to one side of the seed furrow. This places the closing disc to the side of the fluted blade coulter where there is old crop residue. The old crop residue forces the closing disc up out of the soil at times, and lets the covering disc penetrate too deeply into the soil at other times. The operation of covering discs in these conditions result in some seed not being covered with soil and other seed being covered with excess soil, as explained above.